1. Field of the Invention
The invention relates to a device for recording an information carrier of a rewritable type, the information carrier comprising a track and the device comprising recording means for recording an information block in a part of the track from an initial position, the information block representing information in a predefined manner.
The invention further relates to a method of recording an information carrier of a rewritable type, the information carrier comprising a track, and an information block being recorded in a part of the track from an initial position, the information block representing information in a predefined manner.
The invention also relates to an information carrier of a rewritable type recorded in accordance with the method.
The invention also relates to a device for reading an information carrier of a rewritable type recorded in accordance with the method, the device comprising reading means for reading and decoding the information blocks.
2. Description of the Related Art
Such an arrangement, method and information carrier are known from U.S. Pat. No. 5,388.105. The device disclosed therein is suitable for an information carrier of an optically rewritable and readable type, such as, for example, a Compact Disc Erasable (CD-E), which has a rewritable layer of phase-change material. Such information carrier has a preformed track, a so-called pregroove. The pregroove comprises address information and is intended for positioning a write head during the recording process for recording in a track optically readable patterns which represent information. The information is contained in blocks which are recorded in specific parts of the track, so-called sectors, from an initial position depending on the address information. The information is then represented in a certain manner by the optically readable patterns which form the block. This representation includes, for example, a sector identification (ID), a synchronization zone, a data block and error detection and correction data, which information is contained in the data block under a specific coding. A problem with the known device is that the optically readable patterns start differing from the desired form when the information carrier is recorded recurrently, so that the reading quality is degraded. This reduces the useful life of an information carrier.
It is an object of the invention to provide a device in which the deviations of the patterns are counteracted.
For this purpose, the device according to the invention is characterized in that the recording means are arranged for substantially shifting the initial position along the track over a randomly selected distance within predefined boundaries and/or for adapting the manner of representation. The invention is also based on the recognition that the deviation of the patterns formed in recurrent recording strongly depends on the correlation between blocks recorded on the same part of the track, the recording of the same or very similar blocks considerably accelerating the pattern degradation. A small shift of the patterns, such as a few (2 to 3) times the longest written mark used therein was expected to be sufficient. Surprisingly however such a small shift, e.g. of around 32 channelbits, proved insufficient, while a substantial shift, e.g. of at least around 128 bits, was found to be effective.
For this purpose, a method according to the invention is characterized in that the initial position is substantially shifted along the track over a distance arbitrarily chosen within predefined boundaries and/or the manner of representation is adapted.
An information carrier according to the invention is recorded in accordance with said method.
A reading device according to the invention is characterized in that the reading means are arranged for reading the information blocks from positions substantially shifted over a distance arbitrarily chosen within predefined boundaries. Also, or alternatively decoding the information blocks is carried out in accordance with the adapted manner of representation of the information therein.
As a result of the aforesaid measures according to the invention, constantly varying patterns will be recorded on every part of the track, thus counteracting the accelerated degradation. An advantageous effect of this is the lengthening of the useful life of the information carrier. This advantageous effect particularly occurs when customary file management systems are used that rewrite file management information always on the same parts of the track.
An embodiment for the device according to the invention is characterized in that the manner of representation of the recorded information may be recovered from the information block itself when read out. This is advantageous in that the recovery of the information from a read information block is independent of information about the manner of representation stored elsewhere.
A further embodiment for the device according to the invention is characterized in that the manner of representation of the recorded information comprises scrambling with a scramble key which scramble key is included in the information block. This is advantageous in that any correlation between information blocks to be recorded on the same location is reduced with scrambling.
A further embodiment for the device according to the invention is characterized in that the manner of representation of the recorded information comprises including a variable amount of dummy data in the information block, which dummy data is recognizable when read out. The advantage of this is that by recurrently adding a variable amount of dummy data, possibly similar patterns in an information block will be recorded each time at different positions. If the of dummy data is added prior to the information in an information block, old information blocks will be largely overwritten and so invalid portions will not continue to be readable.
A further embodiment for the device according to the invention is characterized in that the manner of representation of the recorded information comprises including a first variable amount of dummy data before and a second variable amount of dummy data following the information in the block, while the sum of the first and second variable amount is substantially constant. The advantage of this is, that the total length of the information block will be substantially constant, allowing recording in a fixed location, while the information content is nevertheless recorded in randomly changing locations.
A further embodiment of the device according to the invention is characterized in that the mode of representation of the recorded information comprises rotating the information over a randomly selected distance in the information block. Information which extends beyond one side of the information block is added to the other side. This is advantageous in that no additional space on the disc is necessary for rotating the information. This is particularly advantageous when synchronization patterns are supplied which shift along with the information and are therefore not always located in the same position.
A further embodiment of the device according to the invention is characterized in that the mode of representation of the recorded information comprises including the randomly selected distance in the respective information block. This is advantageous in that the distance of the rotation of the information can then be simply derived. This is particularly advantageous when synchronization patterns are used which shift along with the information, because in that case the amount of information before the first synchronization pattern and/or after the last synchronization pattern can be determined when read out.
These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter.